wpmail.php

<?php

$ses = Aws\Ses\SesClient::factory(array(
	'key'    => SES_KEY,
	'secret' => SES_SECRET,
	'region' => SES_REGION
));

class SesClientProxyForPHPMailer {
	private $phpmailer;
	public function __construct($phpmailer) {
		$this->phpmailer = $phpmailer;
	}

	public function Send() {
		global $ses;
		$this->phpmailer->preSend();
		try {
			return $ses->sendRawEmail([
				'RawMessage' => [ 'Data' => base64_encode($this->phpmailer->getSentMIMEMessage()) ]
			]);
		} catch (Exception $e) {
			trigger_error($e->getMessage());
			throw new phpmailerException($e->getMessage(), $e->getCode());
		}
	}
}

add_action('phpmailer_init', function(&$phpmailer) {
	$phpmailer = new SesClientProxyForPHPMailer($phpmailer);
});